Linq中委托的实例

List<CustomerRegulationRuleValueChangeDetailList> querychange = (from p in _repository.Change<CustomerRefundChangeValue>().AsQueryable()
                join d in _repository.Change<CustomerRegulationCabin>().AsQueryable() on p.CustomerRegulationCabinId equals d.Id
                join e in _repository.Change<CustomerRegulationRule>().AsQueryable() on p.CustomerRegulationRuleId equals e.Id
                where e.RuleType == 2 && p.CustomerRegulationCabinId == item.Id  orderby e.Sort
                select new CustomerRegulationRuleValueChangeDetailList
                {
                   TableHead = e.TableHeader,
                   Value = p.Value == "0" ? "免费" : (
                   GetQueryrefund(p.Value))
                }).ToList();

 /// <summary>
 /// <param name="data">正则判断，如果是数子则字符串后加%</param>
 /// <returns></returns>
 public static string GetQueryrefund(string data)
        {
            if (!string.IsNullOrWhiteSpace(data))
            {
                const string pattern = "^[0-9]*$";
                Regex rx = new Regex(pattern);
                if (rx.IsMatch(data) == true)
                {
                    return data + "%";
                }
                else
                {
                    return data;
                }
            }
            else
            {
                return "";
            }
        }

根据主键集合删除数据表中的数据，去重

 /// <summary>
 ///主键id集合
 /// </summary>
  public class OutsideFreightRateIds
  {
        /// <summary>
        /// 编号
        /// </summary>
        public List<long?> Ids { get; set; }
  }

OutsideFreightRateIds data = new  OutsideFreightRateIds();
data.Ids = new List<long?>();
data.Ids.add(123);
data.Ids.add(456);
var listredis = (from a in listredis where DelListByListids(a.Id, data)
                                     select a).ToList();

        /// <summary>
        /// 根据泛型集合中的某个属性值集合删除该集合中的元素集合
        /// </summary>
        /// <typeparam name="T"></typeparam>
        /// <param name="id"></param>
        /// <param name="model"></param>
        /// <returns></returns>
        private bool DelListByListids<U, T>(U id, T model)
        {
            bool result = true;
            Type t = model.GetType();
            var list = t.GetProperties().ToList();
            foreach (var itemes in list)
            {
                foreach (var item in (IEnumerable)itemes.GetValue(model))
                {
                    if (id.ToString() != item.ToString())
                    {
                        result = true;
                    }
                    else
                    {
                        result = false;
                        return result;
                    };
                }
            }
            return result;
        }

 定义扩展方法根据某个字段去掉重复

   public class Compare<T, C> : IEqualityComparer<T>
    {
        private Func<T, C> _getField;
        public Compare(Func<T, C> getfield)
        {
            this._getField = getfield;
        }
        public bool Equals(T x, T y)
        {
            return EqualityComparer<C>.Default.Equals(_getField(x), _getField(y));
        }
        public int GetHashCode(T obj)
        {
            return EqualityComparer<C>.Default.GetHashCode(this._getField(obj));
        }
    }

  public static class CommonPareHelper
    {
        public static IEnumerable<T> MyDistinct<T, C>(this IEnumerable<T> source, Func<T, C> getfield)
        {
            return source.Distinct(new Compare<T, C>(getfield));
        }
    }

方法调用：

  var scinfo = list.ToList().MyDistinct(p => p.SensorSerialNum);

或者：

  public class LambdaComparer<T> : IEqualityComparer<T>
    {
        private readonly Func<T, T, bool> _lambdaComparer;
        private readonly Func<T, int> _lambdaHash;
        public LambdaComparer(Func<T, T, bool> lambdaComparer)
            : this(lambdaComparer, EqualityComparer<T>.Default.GetHashCode)
        {
        }
        public LambdaComparer(Func<T, T, bool> lambdaComparer, Func<T, int> lambdaHash)
        {
            if (lambdaComparer == null)
                throw new ArgumentNullException("lambdaComparer");
            if (lambdaHash == null)
                throw new ArgumentNullException("lambdaHash");
            _lambdaComparer = lambdaComparer;
            _lambdaHash = lambdaHash;
        }

        public bool Equals(T x, T y)
        {
            return _lambdaComparer(x, y);
        }

        public int GetHashCode(T obj)
        {
            return _lambdaHash(obj);
        }
    }